1. Field of the Invention
The present invention relates to a low emissivity glass and glass articles made of low emissivity glass, and more particularly, to a low emissivity glass (low-E glass) for use as window glasses for architecture and automobiles and glass articles such as double glazing using low emissivity glass.
2. Prior Art
Generally, different kinds of performance or properties are required of glass for use as window glasses for architecture and automobiles, depending on climate and regional characteristics such as hot or cold weather. Further, the amount of solar radiation energy which penetrates a window glass differs depending on the location and direction in which the window glass is installed, and therefore the performance required of glass also differs depending on the location and direction of installment of the window glass.
For example, in a cold northern region where the weather is severe in winter, the heat insulating property of the glass is important since rooms are heated in winter, while the solar heat shading property of the glass is not considered to be so important. On the other hand, in a hot southern region where the heat is severe, while the heat insulating property is not considered to be so important, it is important that the glass has a solar heat shading property enough to prevent the inflow of solar radiation energy into rooms or or into automobiles, especially in summer.
Further, as to the installation location of the window glass, a larger amount of solar energy penetrates a window glass located on east and west sides of a building or house, which face toward the sun, and thus the window glass to be installed on the east or west side of a building or house needs to have a high degree of solar heat shading. On the other hand, since sunlight does not directly shine a north side of a building or house, solar radiation energy penetrating the window glass is small, and therefore it is preferable to use a window glass having a low degree of solar heat shading.
Conventionally, a window glass formed of a heat insulating glass with an improved solar heat shading property has been proposed in Japanese Laid-Open Patent Publication (Kokai) No. 8-104547 (hereinafter referred to as xe2x80x9cthe first prior artxe2x80x9d), which is comprised of a glass substrate laminated with a layer of Ag and a metallic oxide.
According to the first prior art, a layer of a metallic oxide film sandwiched between two Ag films is laminated on the surface of a glass substrate, to secure required heat insulation, and maintain a high degree of visible light transmittance, securing required transparency of the glass, and further, restrain solar radiation light transmittance, improving the solar heat shading property of the glass. In addition, the metallic oxide is formed of tin oxide or zinc oxide, to keep both the color of transmitting or incident light and the color of reflected light to be achromatic.
Further, the first prior art has proposed a double glazing formed of one or more sheets of the above described insulating glass and has an improved heat insulation when used as a window glass.
However, in the first prior art, since two layers of Ag, which has a high degree of infrared ray reflection, are coated on the surface of the glass substrate, the transmittance rate of solar radiation light is low (60% or less) and therefore the degree of solar heat shading of the glass is extremely high. As a result, when the heat insulating glass according to the first prior art is used on a north side of a building or house, the solar radiation energy inflow into the room is so small that the room becomes excessively cold, leading to an uncomfortable living condition. Especially, in this case where the inflow of solar radiation energy;into the room is small, the room temperature may decrease to a point where it becomes necessary to turn on a heating appliance, causing an unfavorable result in terms of energy saving.
That is, although the first prior art may provide satisfactory results when used in a specific region or in a specific installation location or direction, it may not provide a comfortable living condition depending on the installation location or region.
Further, there has been proposed a switchable light control glass which is formed by causing a substance, which absorbs and reflects light in the visible to near infrared regions, to be precipitated on anisotropic dipolar particles coated with a semiconductor, and then dispersing the anisotropic dipolar particles in a liquid dielectric, whereby the glass can be electrically controlled in absorbance and reflectance (e.g. Japanese Laid-Open Patent Publication (Kokai) No. 64-38732, hereinafter referred to as xe2x80x9cthe second prior artxe2x80x9d).
According to the second prior art, the solar heat shading property may be arbitrarily controlled as required, by electrically controlling the absorbance and reflectance.
In the second prior art, however, cohesion or the like of the anisotropic dipolar particles is prone to: occur, leading to degraded quality reliability. Further, the manufacturing cost is high, which makes the glass unpractical for use as window glasses in architecture and automobiles.
It is therefore an object of the present invention to provide a low emissivity (low-E) glass and glass articles made of the low emissivity glass which permit controlling the solar heat shading property within a certain range without spoiling the transparency and heat insulating property thereof, to thereby realize a comfortable living condition in a wide region of the world or in a wide location of installment.
To attain the above object, the present invention provides a low emissivity glass comprising:
a glass substrate having a surface; and
a plurality of metallic oxide based films comprising metallic oxide and laminated on the surface of the glass substrate;
wherein the plurality of metallic oxide based films include a first tin oxide based film containing antimony (hereinafter referred to as xe2x80x9cSnSbOx filmxe2x80x9d), and a second tin oxide based film containing fluorine (hereinafter referred to as xe2x80x9cSnO2:F filmxe2x80x9d).
By doping a tin oxide based film comprising tin oxide with fluorine (F) to improve electric conductivity and thereby maintain a desired heat insulating property, and by laminating a tin oxide based film doped with antimony (Sb) on the surface of the glass substrate,,it is possible to achieve control of the solar heat shading property of the glass in a certain range, so that the solar heat shading property can be controlled within a certain range without spoiling the heat insulating property, thus making it possible to obtain a low emissivity glass which is suitable for use in various regions and installment at various locations.
Preferably, the SnSbOx film contains antimony in an amount of 0.01 to 0.2 in terms of mole ratio relative to an amount of tin (=Sb mol/Sn mol), to avoid an excessive decrease in visible light transmittance.
By setting the mole ratio in the SnSbOx film to 0.01 to 0.2, the visible light transmittance slightly decreases, however this demerit is overcome by the fact that the film has an absorbing spectrum in the near-infrared region, thus permitting control of the solar heat shading property within a certain range without spoiling the transparency of the glass.
Preferably, the low emissivity glass comprises a tin oxide film consisting essentially of tin oxide (hereinafter referred to as xe2x80x9cSnO2 filmxe2x80x9d) formed on the surface of the glass substrate, and a silicon oxide based film comprising silicon oxide (hereinafter referred to as xe2x80x9cSiO2 filmxe2x80x9d) formed thereon, and wherein at least the SnSbOx film and SnO2:F film are laminated on the SiO2 film, to prevent unevenness in the color of reflected light or the color of transmitting or incident light as well as to enable adjustment of color tone.
In a preferred embodiment of the present invention, the SnSbOx film is formed on the SiO2 film, and the SnO2:F film is formed on the SnSbOx film, and wherein the SnSbOx film contains antimony in an amount of 0.01 to 0.2 in terms of mole ratio relative to an amount of tin. In an alternative preferred embodiment, the SnO2:F film is formed on the SiO2 film, and the SnSbOx film is formed on the SnO2:F film.
By forming metallic oxide films on the glass substrate in the above-mentioned order of lamination, it is possible to obtain a low emissivity glass which is satisfactory in both solar heat shading property and heat insulating property as well as transparency without spoiling the appearance.
In a further alternative preferred embodiment of the present invention, the SnSbOx film is formed on the surface of the glass substrate, the SiO2 film is formed on the SnSbOx film, and the SnO2:F film is formed on the SiO2 film.
Even with this lamination order, it is possible to obtain a low emissivity glass which is satisfactory in both solar heat shading property and heat insulating property as well as transparency and also satisfactory in color tone, making it possible to reduce the number of laminated layers of metallic oxide films and thereby enhance productivity.
Preferably, at least one of the SnO2 film, the SnSbOx film, and the SnO2:F film contains chlorine, to thereby enhance electric conductivity.
In manufacturing the low emissivity glass according to the present invention, it is preferable that the glass substrate is formed from glass in a form of a ribbon formed by causing a glass raw material to flow on molten tin, and a plurality of metallic oxide based films are each formed by depositing a metallic oxide in solid phase on a surface of the glass in the form of a ribbon.
According to the above manufacturing method, it is possible to form films on the glass surface heated to a temperature above its softening point, leading to an improvement in properties of the films, and other properties. Further, productivity is also improved, such that an efficient mass production of low-E glass is realized.
To attain the above object, the present invention provides a glass article comprising a plurality of glass plates, at least one of which is formed of any one of the above-mentioned low emissivity glasses, wherein a plurality of glass plates are arranged in opposed relation to each other with a hollow layer defined therebetween.
It is known that a double glazing unit as a glass article which has a hollow layer such as an air layer, inert gas layer, or reduced pressure or vacuum layer, defined between a plurality of glass plates exhibits very excellent performance in terms of heat insulating property. Therefore, if the glass article according to the present invention is used as window glasses for architecture, it is possible to realize a comfortable living condition by selecting the excellent solar heat shading property or the excellent heat insulating property.
The above and other objects, features and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.